Women on birth control may be at increased risk of blood clots if they catch coronavirus, a new study warns.
COVID-19 increases the risk of blood clots for those taking oral contraceptives, according to the research published Wednesday.
Contraceptive pills contain estrogen which can narrow vessels. Individuals who are pregnant or on HRT (hormone replacement therapy) face the same danger.
Prescribing blood thinners – such as aspirin – to all three groups would offer protection, suggested study co-author Dr Daniel Spratt.
‘During this pandemic, we need additional research to determine if women who become infected during pregnancy should receive anti-coagulation therapy – or if women taking birth control pills or hormone replacement therapy should discontinue them,’ he said.
Coronavirus can cause blood clots to form – even in previously healthy people, said Dr Spratt.
What is more, estrogen fuels potentially deadly deep vein thrombosis in some mothers-to-be – and in women using the pill or HRT.
The blockages usually start in the legs. They can move up, triggering a heart attack or stroke.
Oral contraceptives are known to carry a small risk of the condition – which may be exacerbated by the coronavirus, reports the new study in Endocrinology.
‘If infected with Covid-19, these women’s risk of blood clotting could be even higher,’ the study authors wrote.
Dr Spratt, of Maine Medical Center in Portland, said: ‘Research that helps us understand how the coronavirus causes blood clots may also provide us with new knowledge regarding how they form in other settings and how to prevent them.’
The links between blood clots and COVID-19 – including the effects of estrogen therapy or pregnancy – are complicated.
Dr Spratt said several studies using innovative animal and tissue models will be required to shed light on them.
Birth control pills remain the most popular method of contraception in the UK and the second most popular form in the US – despite alternatives such as injections and implants.
More than nine million American women take them at any one time, despite potential side effects ranging from depression to weight gain.
They also carry up to a fourfold increase in a woman’s chance of developing a blood clot.
Most contain estrogen and a synthetic form of progesterone. These are the hormones that sustain pregnancy and, by imitating the condition, prevent it.
But they also raise clotting factors. For the average woman, the absolute risk of a blood clot just one in a thousand. The coronavirus may raise this significantly.
‘As more information emerges regarding the effects of Covid-19, questions arise as to whether infection aggravates blood clots and strokes associated with combined oral contraceptives and other oestrogen therapies, as well as pregnancy-associated risk,’ said Dr Spratt.
Rates of strokes double from about four to eight in 100,000 young women a year. Similar figures have been found for older women on HRT.
‘In pregnancy, the risk of blood clots increases four to fivefold. The mechanisms for these and the duration of the effect after discontinuing therapy remain unclear,’ saidi Dr Spratt.
‘A common recommendation is to discontinue estrogen-containing preparations two weeks before planned activities that may cause thrombosis such as surgery or long flights.’
He added: ‘Conversations between clinicians, researchers, endocrinologists and haemotologists are necessary to explore potential interactions between Covid-19 and pregnancy or oestrogen therapy that could guide management.’